CN109957076B

CN109957076B - Mud-resistant slump-retaining polycarboxylate superplasticizer and preparation method thereof

Info

Publication number: CN109957076B
Application number: CN201910124365.8A
Authority: CN
Inventors: 刘斌; 李本刚
Original assignee: Jiangsu Wanbang New Material Technology Co ltd
Current assignee: Jiangsu Wanbang New Material Technology Co ltd
Priority date: 2019-02-19
Filing date: 2019-02-19
Publication date: 2021-06-04
Anticipated expiration: 2039-02-19
Also published as: CN109957076A

Abstract

The invention discloses a mud-resistant slump-retaining polycarboxylic acid water reducing agent and a preparation method thereof, wherein a polyether monomer is refluxed with toluene to carry water, and the residual toluene is distilled out through reduced pressure distillation; carrying out end-capping reaction on the dehydrated polyether monomer, furfuryl isocyanate and N-carbamyl maleimide in sequence to obtain a functional end-capped polyether monomer; and mixing the monomer with water, an initiator, a chain transfer agent and acrylic acid, heating for reaction, and adding an alkali solution for neutralization until the pH value is 6-7 to obtain the polycarboxylate superplasticizer mother liquor. The end of the functional end-capped polyether monomer prepared by the invention is connected with a cyclic structure and an amide/imide structure with larger physical size. When the functional end-capped polyether monomer is used for preparing the polycarboxylic acid water reducing agent, the terminal end of the polyether side chain has a larger physical size and a larger ring structure, so that the polyether side chain can be prevented from being embedded into an interlayer of clay, and the mud resistance effect is achieved; the amide/imide structure at the tail end of the polyether side chain can improve the dispersing capacity and slump retaining performance of the polycarboxylic acid water reducer.

Description

Mud-resistant slump-retaining polycarboxylate superplasticizer and preparation method thereof

Technical Field

The invention relates to a mud-resistant slump-retaining polycarboxylic acid water reducer and a preparation method thereof, belonging to the field of concrete functional additives.

Background

The polycarboxylate superplasticizer is a comb-shaped water-soluble polymer consisting of a main chain rich in carboxylic acid groups and sulfonic acid groups and a polyoxyethylene side chain, has the advantages of designable structure, low mixing amount, high water-reducing rate and the like, and is increasingly and widely applied to concrete engineering. With the rapid development of the building industry in China, the consumption of the sandstone is high, high-quality sandstone resources are scarce, and the content of the sandstone and the mud is high. A large number of engineering examples and researches show that the polycarboxylate superplasticizer is very sensitive to the mud content in concrete aggregates, and shows the phenomena of insufficient water reducing rate, large slump loss and the like when the mud content in a concrete system is higher. At present, two methods of super-mixing amount and compounding are generally adopted in the market to solve the problem of high mud content of the sandstone material, so that the additive cost of the single concrete is greatly improved, and the trouble of additional production process is brought. Therefore, from the design of the molecular structure of the polycarboxylate superplasticizer, by introducing functional groups, the high-performance polycarboxylate superplasticizer which is suitable for high-mud-containing aggregates and simple in preparation process is developed, and has important significance for promoting the application of the polycarboxylate superplasticizer in concrete engineering.

An important reason that the polyether type polycarboxylate superplasticizer widely used at present is sensitive to the mud content of concrete aggregates is that the polyether side chains of the polycarboxylate superplasticizer are very easy to be embedded into the interlayer of the clay, so that the polyether side chains lose the dispersing effect on cement particles, the molecular concentration of the effective superplasticizer in unit volume is reduced, the initial fluidity of concrete is reduced, and the fluidity loss is too fast. In order to solve the problem, the invention of chinese patent CN 104710580B adopts macromolecular carboxylic acid to esterify and terminate the terminal hydroxyl group of the polyether monomer, so as to increase the physical size of the terminal, and further increase the physical size of the terminal of the side chain of the molecule of the polycarboxylic acid water reducing agent prepared from the terminated polyether, so that the side chain of the polyether is not easy to enter into the interlayer of the clay, thereby achieving the effect of mud resistance. The method well prevents polyether side chains from being embedded into interlayer of clay, but has the problems that esterification end capping reaction needs high temperature and catalysis, side reaction is easy to occur and the like.

On the other hand, the amide or imide structure is introduced into the polycarboxylate superplasticizer molecules, so that the dispersing capacity and the slump retaining performance of the polycarboxylate superplasticizer can be remarkably improved, and the adaptability of the polycarboxylate superplasticizer to concrete materials is improved, wherein a typical example is an amide/imide type polycarboxylate superplasticizer called a third-generation polycarboxylate superplasticizer (see: the building materials bulletin, 2012, 15 (1): 22-26; the silicates bulletin, 2013, 41 (8): 1079-.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a functional end-capped polyether monomer and is used for preparing a mud-resistant slump-retaining polycarboxylic acid water reducing agent.

In order to solve the technical problem, the invention discloses a preparation method of a mud-resistant slump-retaining type polycarboxylate superplasticizer, which comprises the following steps:

(1) refluxing and dewatering: heating the polyether monomer until the polyether monomer is completely melted, adding toluene accounting for 10-15% of the mass of the polyether monomer, refluxing to carry out water carrying, and distilling under reduced pressure to evaporate the residual toluene after no water is carried out;

(2) blocking by furfuryl isocyanate: adding furfuryl isocyanate into the dehydrated polyether monomer in the step (1), and stirring and reacting for 2-3 hours at the temperature of 70-80 ℃;

(3) n-carbamoylmaleimide capping: adding N-carbamyl maleimide into the product obtained in the step (2), and stirring and reacting at 70-80 ℃ for 3-4 hours to obtain a functional end-capped polyether monomer;

(4) and (3) mixing and heating the functional end-capped polyether monomer obtained in the step (3), water, an initiator, a chain transfer agent and acrylic acid for reaction, and adding an alkali solution for neutralization until the pH value is 6-7 to obtain the mud-resistant slump-retaining polycarboxylic acid water reducer.

Preferably, in the step (1), the polyether monomer is a methallyl polyoxyethylene ether monomer or a isopentenyl polyoxyethylene ether monomer.

The reduced pressure distillation temperature is 55-70 ℃, and the pressure is 10-15 mmHg; the purpose of the reflux water removal is to remove the water content of the polyether monomer as much as possible and to avoid the reaction of the furfuryl isocyanate with water.

Preferably, in the step (2), the ratio of the amount of the furfuryl isocyanate to the amount of the polyether monomer is 0.9-1: 1; the purpose of the furfuryl isocyanate blocking is to introduce a furan ring structure at the end of the polyether monomer in preparation for the next step of N-carbamoylmaleimide blocking.

Preferably, in the step (3), the ratio of the adding amount of the N-carbamyl maleimide to the amount of the polyether monomer is 0.9-1: 1; the purpose of the N-carbamoylmaleimide termination is to introduce a cyclic structure and an amide/imide structure with larger physical size at the end of the polyether monomer.

In the step (4), the initiator can adopt ammonium persulfate-sodium bisulfite or vitamin C (Vc) -hydrogen peroxide; the chain transfer agent can adopt mercaptopropionic acid, thioglycolic acid, mercaptoethanol or sodium hypophosphite.

The functional end-capped polyether monomer is mixed with water, an initiator, a chain transfer agent and acrylic acid according to the mass ratio of 1.5 (310-320): (0.1-0.2): 3.8-4.2.

Wherein water is used as a medium for reaction; the initiator acts on the initial reaction; chain transfer agents are used to control product molecular weight; acrylic acid is used to polymerize small monomers.

Preferably, the heating reaction is carried out at 45-50 ℃ for 5-7 hours under normal pressure.

The mud-resistant slump-retaining type polycarboxylate water reducer prepared by the scheme is also in the protection scope of the invention.

Has the advantages that:

1. the end of the functional end-capped polyether monomer prepared by the invention is connected with a cyclic structure and an amide/imide structure with larger physical size. When the functional end-capped polyether monomer is used for preparing the polycarboxylic acid water reducing agent, the terminal end of the polyether side chain has a larger physical size and a larger ring structure, so that the polyether side chain can be prevented from being embedded into an interlayer of clay, and the mud resistance effect is achieved; the amide/imide structure at the tail end of the polyether side chain can improve the dispersing capacity and slump retaining performance of the polycarboxylic acid water reducer.

2. In the preparation method, the activity of the two-step end capping reaction of the functional end capping polyether monomer is very high, the added furfuryl isocyanate and N-carbamyl maleimide can be almost completely reacted, and subsequent separation and purification are not needed; moreover, the reaction conditions are mild, and side reactions can be effectively avoided.

Drawings

The foregoing and/or other advantages of the invention will become further apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

FIG. 1 is a scheme showing the reaction scheme for the preparation of a functionally terminated polyether monomer.

Detailed Description

The invention will be better understood from the following examples.

Example 1

(1) Refluxing and dewatering: mixing methyl allyl polyoxyethylene ether (HPEG, number average molecular weight M)_n2400) heating to be completely melted, adding toluene accounting for 10% of the mass of the polyether monomer, refluxing to carry out water carrying, and distilling at 60 ℃ under reduced pressure to evaporate the residual toluene;

(2) blocking by furfuryl isocyanate: adding furfuryl isocyanate (the mass ratio of the furfuryl isocyanate to the HPEG monomer is 1:1) into the dehydrated HPEG monomer in the step (1), and stirring and reacting for 3 hours at 70 ℃;

(3) n-carbamoylmaleimide capping: adding N-carbamyl maleimide (the mass ratio of the N-carbamyl maleimide to the HPEG monomer is 1:1) into the product obtained in the step (2), and stirring and reacting for 4 hours at 70 ℃ to obtain a functional end-capped polyether monomer; the specific reaction scheme is shown in figure 1.

(4) And (3) mixing the functional end-capped polyether monomer obtained in the step (3) with acrylic acid, an initiator hydrogen peroxide-Vc (redox ratio: 6.2:1), a chain transfer agent mercaptopropionic acid and water according to the mass ratio of 1.44:4.00:0.13:0.17:312.19, reacting for 7 hours at the temperature of 45 ℃ under normal pressure, and adding an alkali solution to neutralize until the pH value is 6-7 to obtain the mud-resistant slump-retaining polycarboxylic acid water reducer.

Example 2

(1) Refluxing and dewatering: mixing methyl allyl polyoxyethylene ether (HPEG, number average molecular weight M)_n2400) heating to be completely melted, adding toluene accounting for 15% of the mass of the polyether monomer, refluxing to carry out water carrying, and distilling at 60 ℃ under reduced pressure to evaporate the residual toluene;

(2) blocking by furfuryl isocyanate: adding furfuryl isocyanate (the mass ratio of the furfuryl isocyanate to the HPEG monomer is 0.9:1) into the dehydrated HPEG monomer in the step (1), and stirring and reacting for 2 hours at 80 ℃;

(3) n-carbamoylmaleimide capping: adding N-carbamyl maleimide (the mass ratio of the N-carbamyl maleimide to the HPEG monomer is 0.9:1) into the product obtained in the step (2), and stirring and reacting at 80 ℃ for 3 hours to obtain the functional end-capped polyether monomer.

(4) And (3) mixing the functional end-capped polyether monomer obtained in the step (3) with acrylic acid, an initiator hydrogen peroxide-Vc (redox ratio: 6.2:1), a chain transfer agent mercaptopropionic acid and water according to the mass ratio of 1.44:4.00:0.13:0.17:312.19, reacting at the temperature of 50 ℃ under normal pressure for 5 hours, and adding an alkali solution to neutralize until the pH value is 6-7 to obtain the mud-resistant slump-retaining polycarboxylic acid water reducer.

Example 3

(1) Refluxing and dewatering: mixing isopentenyl polyoxyethylene ether (TPEG, number average molecular weight M)_n2400) heating to be completely melted, adding toluene accounting for 10% of the mass of the polyether monomer, refluxing to carry out water carrying, and distilling at 60 ℃ under reduced pressure to evaporate the residual toluene;

(2) blocking by furfuryl isocyanate: adding furfuryl isocyanate (the mass ratio of the furfuryl isocyanate to the TPEG monomer is 1:1) into the dehydrated TPEG monomer in the step (1), and stirring and reacting for 2 hours at 80 ℃;

(3) n-carbamoylmaleimide capping: adding N-carbamyl maleimide (the mass ratio of the N-carbamyl maleimide to the TPEG monomer is 1:1) into the product obtained in the step (2), and stirring and reacting at 80 ℃ for 3 hours to obtain the functional end-capped polyether monomer.

Example 4

(1) Refluxing and dewatering: mixing isopentenyl polyoxyethylene ether (TPEG, number average molecular weight M)_n2400) heating to be completely melted, adding toluene accounting for 15% of the mass of the polyether monomer, refluxing to carry out water carrying, and distilling at 60 ℃ under reduced pressure to evaporate the residual toluene;

(2) blocking by furfuryl isocyanate: adding furfuryl isocyanate (the mass ratio of the furfuryl isocyanate to the TPEG monomer is 0.9:1) into the dehydrated TPEG monomer in the step (1), and stirring and reacting for 3 hours at 70 ℃;

(3) n-carbamoylmaleimide capping: adding N-carbamyl maleimide (the mass ratio of the N-carbamyl maleimide to the TPEG monomer is 0.9:1) into the product obtained in the step (2), and stirring and reacting for 4 hours at 70 ℃ to obtain the functional end-capped polyether monomer.

Example 5

In this example, a concrete experiment was performed using the mud and slump loss resistant polycarboxylic acid water reducing agent described in example 4. For comparison, a common polycarboxylate superplasticizer is prepared by the following steps: using the same amount of prenyl polyoxyethylene ether (TPEG, number average molecular weight M)_n2400) was used instead of the functional end-capped polyether monomer, the general polycarboxylic acid water reducing agent was prepared according to the method described in the step (4) in example 4.

The concrete experiment adopts PO42.5 cement of Jiangsu Helin cement plant: the 3-day intensity was 27.8MP, the 28-day intensity was 47.3 MP; the mineral powder is Nanjing Meibao, the grade is S95, and the activity index is measured to be 101; the fly ash is Nanjing Huaneng second-grade coal ash, and the water demand ratio is measured to be 99; the sand is natural sand, and the fineness modulus of the sand is 2.5; the stones were 5-25 continuous graded and the crush value was measured to be 8. According to the existing materials, the mixing proportion of common C30 concrete is selected, as shown in Table 1:

TABLE 1

Cement/kg	Mineral powder/kg	Coal ash/kg	Sand/kg	Stone/kg	W/kg	Additive/kg
							240	60	50	770	1070	175	5.25

In order to simulate the mud content of the sand, the dry mud blocks are crushed and then sieved by a 75-micron sieve to obtain mud powder, the mud powder is manually used for replacing the sand, and the mixing ratio is shown in table 2:

TABLE 2

According to the concrete test scheme, the concrete performance and strength test results of the common polycarboxylate superplasticizers for comparison are shown in table 3, and the concrete performance and strength test results of the mud-resistant slump-retaining polycarboxylate superplasticizer described in example 4 are shown in table 4:

TABLE 3

TABLE 4

As can be seen from the experimental results of tables 3 and 4: the higher the sand content is, the poorer the working performance of the concrete is, and the greater the strength loss of the concrete is; for a common polycarboxylic acid water reducing agent, when the mud content of sand exceeds 5%, the working performance of concrete is greatly influenced, and when the mud content exceeds 7%, the concrete basically has no working state, and the influence on the strength of the concrete in 7 days and 28 days is large; the mud-resistant slump-retaining type polycarboxylate water reducer described in example 4 can maintain good workability even when the sand contains 9% of mud, and the strength loss of concrete is smaller than that of the concrete using a common polycarboxylate water reducer. Therefore, the mud collapse resistant polycarboxylic acid provided by the invention has good mud collapse resistant effect.

The invention provides a thought and a method for a mud-resistant slump-retaining polycarboxylic acid water reducer and a preparation method thereof, and a plurality of methods and ways for realizing the technical scheme are provided. All the components not specified in the present embodiment can be realized by the prior art.

Claims

1. A preparation method of a mud-resistant slump-retaining polycarboxylate superplasticizer is characterized by comprising the following steps:

2. The preparation method of the mud-resistant and slump-resistant polycarboxylate water reducer as claimed in claim 1, wherein in the step (1), the polyether monomer is a methyl allyl polyoxyethylene ether monomer or a isopentenyl polyoxyethylene ether monomer.

3. The preparation method of the mud-resistant and slump-resistant polycarboxylic acid water reducer as claimed in claim 1, wherein in the step (1), the temperature of reduced pressure distillation is 55-70 ℃, and the pressure is 10-15 mmHg.

4. The preparation method of the mud and slump loss resistant polycarboxylate superplasticizer according to claim 1, wherein in the step (2), the mass ratio of the furfuryl isocyanate to the polyether monomer is 0.9-1: 1.

5. The preparation method of the mud and slump loss resistant polycarboxylate water reducer as claimed in claim 1, wherein in the step (3), the ratio of the addition amount of the N-carbamylmaleimide to the amount of polyether monomer is 0.9-1: 1.

6. The preparation method of the mud-resistant and slump-resistant polycarboxylic acid water reducer as claimed in claim 1, wherein in the step (4), the initiator is sodium hydrogen sulfite ammonium persulfate or vitamin C-hydrogen peroxide.

7. The preparation method of the mud and slump loss resistant polycarboxylate water reducer as claimed in claim 1, wherein in the step (4), the chain transfer agent is mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol or sodium hypophosphite.

8. The method for preparing the mud and slump loss resistant polycarboxylate water reducer as claimed in claim 1, wherein in the step (4), the functional end-capped polyether monomer is mixed with water, an initiator, a chain transfer agent and acrylic acid according to the mass ratio of 1.5 (310-320): (0.1-0.2): 3.8-4.2).

9. The method according to claim 1, wherein in the step (4), the heating reaction is carried out at 45-50 ℃ for 5-7 hours under normal pressure.

10. The mud-resistant slump-retaining type polycarboxylate water reducer prepared by any one preparation method of claims 1-9.